Earthships are earth-sheltered autonomous buildings made of tires rammed with earth, which are usually arranged in U-shaped or horseshoe-shaped modules. Each tire is rammed full of earth manually using a sledge hammer. Windows on the sunny side admit light and heat. The open end of the U-shaped structure faces south in the northern hemisphere, and north in the southern hemisphere, so that the house will catch maximum sunlight in the colder months. An earthship is designed to interface with its environment wherever possible and to create its own utilities.
Internal, non-load-bearing walls are often made of a "honeycomb" of recycled cans separated by concrete. The walls are then usually thickly plastered, using the pull-tabs on the cans as a lath to hold the adobe and stucco. This is known as a tin can wall.
The earthship, as it exists today, began to take shape in the 1970s. Mike Reynolds, founder of Earthship Biotecture, a company that specializes in designing and building earthships, wanted to create a home that would do three things. First, it would be sustainable. It would use material indigenous to the entire planet as well as reuse materials wherever possible. Second, his homes would generate their own utilities and be independent from the grid so they would be less susceptible to natural disasters and free from the electrical and water grids that Reynolds considered ugly. Finally, it would be available. He wanted to create a home that the average person with no specialized construction skills would be able to create.
Eventually, his vision took the form of the common U-shaped earth-rammed tire home seen today. However, as a concept, the Earthship is not limited to earth-rammed tires. Any dense material with a potential for thermal mass, such as concrete, adobe, or stone can be used to create an Earthship. However, the earth-rammed tire version of the Earthship is now the most common for several reasons, and is usually the only structure referred to as Earthship.
Unlike other materials, rammed-earth tires are more accessible to the average person. Scrap tires are ubiquitous around the world and easy to come by; there are an estimated 2 billion tires in the US. According to the Scrap Tire Management Council, as many as 253 million scrap tires are generated each year in the US, and of those 253 million tires only 53% are reclaimed by the scrap tire market. The method by which the scrap tires are converted into usable "bricks"—the ramming of the earth—is simple and affordable.
The rammed-earth tires of an earthship are usually assembled by teams of two people working together as part of a larger construction team. One member of the two-person team shovels dirt, which usually comes from the building site, placing it into the tire one scoop at a time. The second member, who stands on the tire, uses a sledge hammer to pack the dirt in. The second person moves in a circle around the tire to keep the dirt even and avoid warping the tire. All tires in an earthship are made in place because, when properly made, they weigh as much as 300 pounds and can be very difficult to relocate.
A fully rammed tire, which is about 2 ft 8 in. wide, is massive enough to surpass conventional requirements for structural load distribution to the earth. Because the tire is so dense, it does not burn when exposed to fire. In 1996, after a fire swept through and destroyed many conventional homes in New Mexico, an earthship was discovered in the aftermath relatively unharmed. Only the south-facing wall and the roof had burned away, compared to the total destruction of the conventional homes.
Currently, earthships are in use in almost every state in the US, as well as many countries in Europe. The use of insulation on the outside of tire walls, which was not common in early designs, is improving the viability of earthships in every climate without compromising their durability. In the year 2000, Mike Reynolds, in partnership with Daren Howarth, launched Earthship Biotecture Europe, an organization that aims to develop the concept of the earthship within a European context.
The Greater World Community is a housing development in Taos, New Mexico, that consists entirely of earthships. The Greater World became a legal subdivision in 1998, and is now phasing its development so that building can continue in certain sections of the development. The project was designed to create an ideal condition from which a sustainable community can grow and flourish. This whole community produces their own energy, harvests their own water, contains and treats their own sewage, manufactures bio-diesel, and grows a great deal of their own food. The buildings also heat and cool themselves, all the while utilizing discarded materials.
The first official earthship home in Europe was built in a small French village called Ger. The home, which is owned by Kevan and Gillian Trott, was built in April 2007 by Kevan, Mike Reynolds, and an Earthship Crew from Taos. The design was modified for a European climate and is seen as the first of many for the European arena.
Earthship Biotecture has finalized plans for a planning application to build on a valuable development site overlooking the Brighton Marina in the UK. The application follows the successful six-month feasibility study funded by the UK Environment Agency and the Energy Savings Trust. The application calls for sixteen one-, two-, and three-bedroom earthship homes on this site. The homes are all designed according to basic earthship principles developed in the US. To construct these homes, 15,000 tires will be recycled. Considering the fact that the UK burns approximately 40 million tires each year, the project represents a progressive step for the earth's environmental health. The plans include the enhancement of habitats on the site for lizards that already live there, and, in fact, the project is being called "The Lizard." This will be the first development of its kind in Europe, and successful development in Brighton may help to pave the way for similar projects around the UK and other European countries.
The earthship was designed as a structure that would exist in harmony with its environment and be free from reliance on centralized utilities. It is important that the earthship create its own utilities as well as use readily available and sustainable materials. In order to be entirely self-sufficient, the earthship needs to be able to handle three key systems: water, electricity, and climate.
Earthships are designed to catch and use water from the local environment without bringing in water from a centralized source. Water used in an earthship is harvested from rain or snow. As water collects on the roof, it is channeled through a silt-catching device and into a cistern. The cisterns are positioned so that they gravity-feed a water organization module (WOM) that filters out bacteria and makes water suitable for drinking. Water is then pushed into a conventional pressure tank to create common household water pressure. Water collected in this fashion is used for any household activities except flushing toilets.
Treating and Reusing Greywater
Greywater, water that has been used and is unsuitable for drinking, is used within the earthship for a multitude of purposes once it is reclaimed. First, before the greywater can be reused, it is channeled through a grease and partical filter/digester and into a 30–60 in. deep rubber-lined botanical cell, a miniature living machine, within the earthship. Oxygenation, filtration, transpiration, and bacteria encounter all take place within the cell and help to cleanse the water. Within the botanical cell, filtration is achieved by passing the water through a mixture of gravel and plant roots. Due to the nature of plants, oxygen is added to the water as it filters, while nitrogen is removed. Water taken up through the plants and transpired at their tops helps to humidify the air. In the cell, bacteria will naturally grow and help to cleanse the water.
Water from the low end of the botanical cell is then directed through a peat moss filter and collected in a reservoir or well. This reclaimed water is then passed once more through a greywater board and used to flush conventional toilets.
Treating and Reusing Black Water
Black water, water that has been used in a toilet, is not reused within the earthship. Instead, blackwater is sent to a solar-enhanced septic tank that is often called the incubator. The solar-enhanced septic tank stores the sun's heat in its concrete mass, which is insulated, to help the anaerobic process. Water from the incubator is channeled out to an exterior landscaping planter cell that is similar to the botanical cell used in greywater treatment.
Earthships are designed to collect and store their own energy from a variety of sources. The majority of electrical energy is harvested from the sun and wind. Photovoltaic panels and windmills located on or near the earthship generate DC energy that is then stored in several types of deep cycle batteries. Additional energy, if required, can be obtained from gasoline-powered generators or by integrating with the city grid.
Conversion and Use
In an earthship, a power organizing module (POM) is used to take stored energy from batteries and invert it for AC use. The POM is a prefabricated system that is simply attached to a wall on the interior of the earthship and wired in a conventional manner. The energy run through the POM can be used to run any household appliance, including washing machines, computers, kitchen appliances, printers, vacuums, etc. None of the electrical energy in an earthship is used for heating or cooling.
The interior climate of an Earthship is stabilized and made comfortable by taking advantage of many phenomena. Mainly, the earthship tries to take advantage of the properties of thermal mass and passive solar heating and cooling.
The load-bearing walls of an earthship, made from tires rammed with earth, provide a dense thermal mass that will soak up heat during the day and radiate heat during the night, keeping the interior climate relatively comfortable all day. Some earthships may also be earth sheltered. The benefits of earth sheltering are twofold: It adds to the thermal mass, and, if the earthship is buried deep enough, it allows the structure to take advantage of the earth's stable temperature.
Passive Solar Heating and Cooling
The earthship is designed in such a way that the sun provides heating, ventilation, and lighting. To take advantage of the sun, an earthship (in the northern hemisphere) is positioned so that its southern wall, which is nonstructural and made mostly of glass sheets, faces directly south. This positioning allows for optimum solar exposure.
To allow the sun to heat the mass of the earthship, the southern wall is angled so that it is perpendicular to light from the winter sun. This allows for maximum exposure in the winter, when heat is wanted, and lesser exposure in the summer, when heat is to be avoided. Some earthships, especially those built in colder climates, use insulated shading on the southern wall to reduce heat loss during the night.
Earthships rely on a balance between the solar heat gain and the ability of the tire walls and subsoil to transport and store heat. The design intends to require little if any auxiliary heat. Some earthships have suffered from over-heating and some from over-cooling, due to a failure to adjust for local conditions.
Some earthships appear to have serious problems with heat loss. In these cases heat appears to be leaking into the ground constantly during the heating season and being lost. This situation may have arisen due to the mistaken belief that ground-coupled structures (building in thermal contact with the ground) do not require insulation. The situation may also be due to large climatic differences between the sunny, arid, and warm southwestern United States, where earthships were first built, and the cloudier, cooler, and wetter climates where some are now being built. Malcolm Wells, an architect and authority on earth-sheltered design, recommends R-value 10 insulation between deep soils and heated spaces. Wells's insulation recommendations increase as the depth of the soil decreases.
In very limited and specific situations, uncommon during the heating season, thermal mass can marginally increase the apparent R-value of a building assembly such as a wall. Generally speaking, thermal mass and R-value are distinct thermodynamic properties and should not be equated. Thermal performance problems apparently seen in some earthship designs may have occurred due to thermal mass being erroneously equated to R-value. According to the Kansas State University Extension Service, the R-value of soil is about 1 per foot.
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